Looking at my MAF sensor (which I'm believing is faulty), I see AFH50M-04 on top, and C6X09 below that.

Online, I'm finding matches for the top number, but none for the bottom(closest was C7X09).
Does the bottom number matter at all?

I believe the top number is the only one you need to worry about.

excellent! This is going to be a lot cheaper then.

When buying a MAF sensor, would a junkyard one be okay?

Inspect it first. Check the wire.

See, mine isn't even dirty(or if it is, it'* so gunked on it looks like it'* part of it haha...cleaned it with cleaner several times to no real affect), but I stall out every 8 tenths of a mile or so, and didn't stall at all with it unplugged. Engine code (before I unplugged, duh ) was the MAF 102 code, and I've replaced vacuum lines and stall worse.

So I'm going to replace it and see what happens. I'll bring mine and compare it to the junkyard ones and see if they look cleaner.